1. Field of the Invention
The present invention generally relates to optical switching. More particularly, the present invention relates to a micro-electro-mechanical-system optical switch actuator having an electrically conductive anchor assembly.
2. Technical Background
In the development of communications technologies, the primary objectives have always included the improvement of transmission fidelity, the increase of data rates, and the increase of distance between relay stations. The speed at which light travels and its potential to address all of these concerns logically led to attempts at optical communication. Early experiments with optical communications suggested the feasibility of modulating a coherent optical carrier wave at very high frequencies, but were commercially impractical because of the installation expense and the tremendous cost of developing the necessary components. The combination of semiconductor technology, which provided the necessary light sources and photodetectors, and optical waveguide technology, however, eventually enabled the development and use of optical fiber-based systems despite these initially perceived difficulties.
Optical networking involves the management and coordination of various functions such as optical transport and optical switching. Earlier approaches to optical switching actually involved the conversion of optical signals into electrical signals and the switching of the electrical signals. This type of electrical/optical conversion proved to be both difficult to implement and costly due to the required transformation into and out of the electrical domain. As a result, more recent approaches have attempted to perform switching in the optical domain.
Optical switching in the networking context presents its own set of unique concerns. For example, in order to efficiently manage the increasing number of optical signals and wavelength channels, optical switches must be significantly reduced in size. Micro-electro-mechanical-systems (MEMS) have recently been developed based on semiconductor processes, and applied in the areas of medicine, life science, sensors, aerospace, micro-satellites and data storage. MEMS technology allows conventionally large components to be reduced to sizes not previously available. While some attempts have been made at applying MEMS technology to optical switching in the networking context, certain concerns still remain.
One such concern is the design of the actuator for the optical switch. For example, thermal actuation schemes have been attempted, but often lead to difficult heating issues. In fact, the type of driving force that is used to operate the actuator is a crucial factor. It is therefore desirable to provide a MEMS optical switch actuator that does not use heat as a driving force.
While certain attempts have been made using electrostatic forces to actuate the optical switch, there is considerable room for improvement. For example, in the conventional electrostatic actuator approach, a pair of electrodes and various anchoring structures will be used to force a reflective element into and out of the path of an optical signal. The anchoring structures serve to attach the actuator to the optical circuit and provide the requisite stability for actuation. These approaches have typically been quite complex and require several fabrication steps in order to create the relatively high number of anchors and complex electrodes. It is therefore desirable to provide a MEMS optical switch actuator that operates in response to electrostatic driving forces, but does not require separate electrode and anchor assemblies.
As noted above, fabrication of MEMS actuators has proven to be quite difficult. For example, in order to generate sufficient force to manipulate a mirror (or reflective element), it is often necessary to provide a multi-level reflection assembly. Specifically, anchoring of the entire structure as well as manipulation of the mirror require widely varying amounts of structural support. Conventional actuators, however, have not addressed this issue to a sufficient level of specificity. It is therefore desirable to provide a method for fabricating a multi-level reflection assembly having an anchor assembly that also functions as an electrode.
In accordance with the present invention, a micro-electro-mechanical-system (MEMS) optical switch actuator is provided. The actuator has a reflective element assembly and a first electrode assembly for moving the reflective element assembly from a first position to a second position based on a switching signal. The actuator further includes an anchor assembly coupled to the reflective element assembly such that a spring force is generated in the reflective element assembly when the reflective element assembly is in the second position. The anchor assembly is electrically conductive such that the switching signal generates an electrostatic force between the anchor assembly and the first electrode assembly. Using the anchor assembly as an effective second electrode allows simplification of the actuator in a manner unachievable under conventional approaches.
In another aspect of the invention, a method for fabricating a MEMS optical switch actuator is provided. The method includes the step of coupling a multi-level reflection assembly to an optical circuit. The reflection assembly has an electrically conductive anchor assembly positioned at a first level with respect to the optical circuit, and a mirror positioned at a second level with respect to the optical circuit. An insulative mirror beam layer is then coupled to the reflection assembly, and an electrode assembly is coupled to the mirror beam layer. The electrode assembly is coupled such that a voltage potential between the anchor assembly and the electrode assembly causes the electrode assembly to force the mirror beam layer and the mirror from a first switching position to a second switching position. Positioning the anchor assembly at a different level from the mirror reduces the overall number of components and allows the fabrication process to be simplified beyond that available under conventional approaches.